prescribing for presbyopia

Bio-Inspired Products for Presbyopia

BY CRAIG W. NORMAN, FCLSA

The process of developing products and devices by taking inspiration from nature is quite interesting. This process, termed bio-inspired or bio-mimetics, aims to mimic the structures, materials and other processes that are seen in nature. It's based on the premise that performance, efficiency, material use and the decrease or elimination of waste can be better managed by mimicking some animal, plant or structure in nature.

There are a couple of obvious bio-inspired concepts to which we can all relate. One is the robot, which is functionally designed to replicate human movements and tasks. Another is the airplane. Aeronautical engineers have been studying the flight of birds for almost a century in an attempt to improve aircraft designs.

Oddly enough, it may be that scientists can look at another area of nature to mimic for contact lens use.

You may have only recently become aware of the Gecko through a TV advertising campaign, used by a national insurance company, that seems to run hourly. But scientists have been studying this lizard, which boasts more than 2,000 different species, for years.

So where does this fit in for future designs of presbyopic contact lenses?

As has been well documented in this column over the past few years, presbyopic contact lens patients pose many challenges. Here are two areas that may be helped by mimicking nature.

Improved Multifocal Designs

The nocturnal helmet gecko has the ability to discriminate colors in dim moonlight while we humans are color-blind in this situation. The optics and the large cones of this gecko are important reasons for their ability to use color vision at low light intensities. Researchers have used photorefractometry and an adapted laboratory Hartmann-Shack wavefront sensor to show that the optical system of the helmet gecko has distinct concentric zones of different refractive powers, creating a multifocal optical system where these zones differed by up to 15 diopters. While these evaluations have been mostly in the area of color vision, could further study in this area be the answer to our search for the ultimate presbyopic lens design? Could we finally be able to engineer multifocal optics that will work regardless of pupil size and amount of lens movement?

Better Wetting Surfaces

Other studies of geckos have focused on the ability of their footpads to stick to surfaces, creating a Van der Waals forces effect. Van der Waals forces describe attractions between atoms, molecules and surfaces. Could studies in this area result in better lens materials that truly provide the improved wetting characteristics that chemists have been searching for in both soft and GP polymers? Can new materials actually get tears to stick to their surfaces? If so, could this be the answer to end-of-day comfort issues, resulting in less presbyopic lens dropouts from contact lens-induced dry eye?

As a clinician, I don't have the scientific background to know if this is possible or not, but maybe the answers to our more complex challenges in contact lenses can be solved by simply looking to nature for bio-inspiration.

Stay tuned — there could be some very interesting products in the not-too-distant future. CLS

Craig Norman is director of the Contact Lens Section at the South Bend Clinic in South Bend, Indiana. He is a fellow of the Contact Lens Society of America and is an advisor to the GP Lens Institute. He is also a consultant to B+L.